The only people who have ever taken the word cracker seriously is niggers. They WANT it to piss us off so fucking badly, but it just doesn't.
And what really pisses them off is when you call them out. Because they'll say "It's not a SERIOUS slur!" and I'll remind them that neither is Sambo, or Darkie, or Jigaboo, or Moon Cricket, or Groid, or Jungle Bunny, or Melon Muncher. None of those will offend a black man nearly as much as the dreaded Nigger word, and yet they'll still get pissed off if you say ANY of them because the slurs are born from racism.
But cracker, despite being another minor and relatively inoffensive slur, is also born of racism. Doesn't matter if it offends the target, you're still a racist for using it.
And they REALLY hate that. They hate having their most potent weapon, accusations of racism, ripped from their hands and rammed up their asses. And they'll make all sorts of excuses about how not only is it not racist, black people can't be racist at all because muh redefinition.